Anchor rod supporting is a main coal roadway supporting method. At present, the two sides of coal roadway are supported with a resin anchoring technique, which has the following problems: firstly, resin anchoring agents have poor adaptability to coal mass and attain a poor anchoring effect, because coal mass is soft and loose and may have high deformation; secondly, severe side falling may occur because the anchor bonding force is too low to restrain the coal mass from getting loose and deforming; thirdly, drilling in coal walls may result in hole collapse easily and has a low probability of hole formation, the resin anchoring agent is inconvenient to apply, and the coal dust may be mixed with the anchoring agent and thereby further reduces anchoring effect; fourthly, the roadway tunneling speed is severely limited owing to a large number of process steps; fifthly, the rod body has fixed length, and has poor adaptability to local areas; sixthly, the one-time side support can't be reinforced to work further once it fails; instead, a new support has to be erected again. Consequently, the roadway has to be expanded repeatedly, the engineering workload is increased, and it is difficult to meet the requirements of succession of tunneling and mining for the novel mine; and it is also difficult to meet the requirements of quick tunneling technique that integrates excavation and anchoring.
Common self-drilling and self-anchoring anchor rods are difficult to apply in coal roadways owing to their complex structure, high cost, and long installation time, etc. The Chinese Patent document CN1054433150A has put forward a self-drilling anchor rod that can be mounted quickly for grouting support. However, a great deal of coal dusts produced by rotary drilling of a drill bit at a high speed can't be discharged timely because the coal dust discharge channel is narrow; in addition, the anchor rod has complex structure and high manufacturing cost. The Chinese Patent document CN1548659A has put forward a method for supporting soft soil layer with self-drilling anchor rods. However, that method can't meet the requirements for coal roadway supporting because the anchor rods cannot be pre-tightened until the grout is cured in the subsequent grouting process. The Chinese Patent Document CN100497887C has put forward a casing and expansion shell type self-drilling hollow anchor rod for roof grouting. However, the effect of the expansion shell mechanism is limited by the coal dusts and crushed stones in the cross bores in the sides; in addition, that method is only applicable to roof, and is not effective to prevent side falling.
At present, a resin cartridge anchor supporting technique is used for coal roadway sides. However, the resin anchoring agent has poor adaptability to soft and loose coal body, side falling and hole collapse may occur easily at the coal walls, and the resin cartridge is inconvenient to mount; the one-time side support can't be reinforced to work further once it fails; instead, a new support has to be erected; consequently, the roadway has to be expanded repeatedly, and the engineering workload is increased; in addition, the requirement for the anchorage length of the anchor rods may vary, depending on the site operation conditions of equipment (e.g., roadheader with anchor, etc.) and the local geologic conditions of the roadway, but the anchor rod length and anchorage length can't be adjusted at present; moreover, the roadway tunneling speed is limited by procedures such as drilling, charging, anchor rod erection, and pre-tightening, etc. There is an urgent need for an efficient and simple supporting method for coal roadway side supporting.